The present invention relates to a tire satisfying both of the reduction of rolling resistance and the improvement of strength of the tire.
The low fuel cost of a car has been conventionally carried out by the reduction of the rolling resistance of a tire (improvement of the rolling resistance performance). Request for the low fuel cost of a car has been recently strengthened increasingly and more superior low heat build-up property is requested. For example, as a method of reducing the rolling resistance of a tire, there is carried out a method of reducing the loss tangent tan δ of tread, sidewall, breaker rubber and clinch in order in which rubbers used are much.
As trial of reducing the rolling resistance of tire member, for example, it is described in the patent literature 1 that a butadiene rubber modified with tin is used for a rubber composition for sidewall as a rubber component, and it is described in the patent literature 2 that a styrene-butadiene rubber modified with solution polymerization and/or a butadiene rubber modified with tin is used as the rubber component of a rubber composition for covering carcass.
As a method of reducing the loss tangent tan δ of a sidewall rubber, there are mentioned a method of reducing the compounding amount of filler, a method of enlarging the particle diameter of carbon black and a method of compounding a modified butadiene rubber, but elongation at break is lowered. Further, as a method of reducing the loss tangent tan δ of a clinch rubber, there are also mentioned a method of reducing the compounding amount of filler, a method of enlarging the particle diameter of carbon black and a method of compounding a modified butadiene rubber, but elongation at break is also lowered; therefore it provokes damage by stone curb and damage at assembling rim and further, causes the friction of rim chafing.
Namely, it is difficult to satisfy both of the reduction of rolling resistance and the improvement of elongation at break and there was no tire having low rolling resistance and superior strength.
[Patent literature 1] Japanese Unexamined Patent Publication No. 5-320421
[Patent literature 2] Japanese Unexamined Patent Publication No. 2007-161819